1. Technical Field
Embodiments generally relate to systems using transponders, that is, transceivers (generally mobile), capable of communicating in a contactless and wireless manner with a terminal.
Embodiments more specifically relate to the optimization of the speed of processing by digital circuits (processor) of a transponder.
2. Discussion of the Related Art
Electromagnetic transponder systems are more and more used, and transponders perform operations of increasing complexity by means of digital processing circuits (in practice, microprocessors). The emergence of mobile telecommunication devices equipped with near-field communication (NFC) routers takes part in this evolution.
It is known that the higher the operation frequency of a processor or a digital processing circuit, the higher its power consumption. It has already been provided to assess the voltage recovered by a transponder in order to deduce the power transferred from a terminal to the transponder.
The transponder however recovers a power supply voltage which depends significantly on the coupling between the terminal and the transponder, and thus on the power consumption of the transponder circuits. This coupling, which is inversely proportional (non linear) to the distance between the terminal and the transponder, conditions the amplitude of the voltage recovered by the transponder.
It is further known that a decrease in the load (transponder power consumption) causes an increase in the voltage and in the remote-supply power. According to the current value of the coupling with respect to the optimum coupling, a load decrease may result in having the coupling tends towards its critical optimum value. The transponder then is in a paradoxical situation where its circuits consume less power but where the voltage and the remote-supply power reach a maximum.
However, for the same value of the recovered voltage, there may be two different coupling situations. Accordingly, it is particularly difficult to determine at which frequency the digital circuits of the transponder are to be operated according to the measured voltage since it is actually risked, while hoping to improve the situation, to worsen it or even to place the transponder in a situation where the drop in the voltage that it receives makes it non-functional.